Robust Method for the Rotor Unbalance Estimation

Several researchers have proposed many methods for balancing the rotor to reduce the machine vibration. Broadly these methods can be categorized into two classes – balancing using measured responses only (known as Influence Coefficient Method) Approach), and balancing using both measured responses and a mathematical (often finite element (FE)) model of rotating machine (Modal Balancing Method). Both of these methods require several trial run-down runs of machine to estimate the unbalance masses and phases at multi balancing plane and usually a substantial experience in field balancing is also required. In addition to this for Modal Balancing a reliable model of the machine is also important which is often difficult to construct. Considering these practical difficulties a method has been developed recently which found to have the potential for fast and reliable rotor unbalance estimation. The method just uses measured pedestal vibration from a single run-down of a machine along with a priori models of the rotor and fluid bearings but the method accounts for the dynamics of the foundation. The method has been qualified on an experimental rotating rig and now the sensitivity analysis has been carried out and presented here for the proposed method with the perturbation errors in the rotor and fluid bearing models to confirm the robustness of the method. 1